Mortice locks for hinged security screen doors and the like often have two or more of the following modes, namely a passage mode, a safety mode and a deadlocked mode.
In the passage mode the lock is effectively “unlocked” such that the door can be opened from either side without the need for a key, simply by operating the handle on one side or other of the door.
In the safety mode, it is possible to operate the lock (often by returning the lock to the passage mode) from one side of the door (typically the inside) without the need for a key. However, it is not possible to operate the lock in any way from the other side (typically the outside) except by using a key. Locks having a safety mode typically incorporate a snib mechanism which is operable from one side of the door (again typically the inside). When the snib mechanism is engaged (i.e. when the lock is “snibbed”), the handle on the other side (the outside) of the door becomes locked/inoperable. However, often the lock's key barrel mechanism is capable of overriding the snib mechanism. In these locks it is possible to open the door from the other side (i.e. the outside) when the lock is in the safety mode by operating the key barrel to disengage the snib mechanism. The operation of the key barrel to disengage the snib may, or may not, return the lock to the passage mode.
In the deadlocked mode, it is not possible to operate the lock from either side except by using a key. Therefore, to open the door when the lock is in the deadlocked mode (irrespective of which side of the door the user is on) a key must be inserted into the lock's key barrel to operate the key barrel mechanism and unlock the lock. In some locks which have a deadlocked mode, operation of the key barrel in this way unlocks and un-latches the lock (i.e. allowing the door to swing open), whereas in other locks the operation of the key barrel merely returns the lock to the passage mode and it is then necessary to also operate the door handle (on one side or other) to open the door.
Locks exist which are convertible between two of the above modes; typically the passage mode and the safety mode, or the passage mode and the deadlocked mode. There are also some locks which are convertible between all three modes.
A problem with these existing locks is that the mechanisms for converting between the modes is often complex. Such complexity can lead to a high parts count, consequent manufacturing and assembly difficulties, and increased manufacturing costs.
Another problem with many existing multimode locks, and indeed other forms of locks as well, is that the lock configuration, or the configuration of its mechanism, results in the lock being “handed”. A lock is “handed” if its design is such that it can only be used on right-handed doors, or only on left-handed doors, but not both. FIGS. I, II, III and IV provide illustrations defining right-handed and left-handed doors respectively. FIGS. I and II provide the relevant definitions for hinged doors, and FIGS. III and IV provide the relevant definitions for sliding doors. Recall that locks in accordance with the invention could be implemented in a range of hinged or sliding door or window applications.
Non-handed locks (i.e. locks which can be used, or which can be configured for use, on either left-handed or right-handed doors as required) have previously been proposed. However, many of these have been simple locks with limited functionality.
Another problem often associated with locks for swinging doors relates to the linearly reciprocating form of lock bolts or “lock tongues” typically used in such locks. Many locks for sliding doors conventionally incorporate a lock tongue which slides laterally (linearly) in and out relative to the lock. More specifically, such lock tongues typically slide between a retracted position where the lock tongue is retracted wholly or partially into the lock to allow the door to be opened, and an extended position where the lock tongue extends or projects relatively further out from the lock and can engage with a strike in the doorjamb to prevent the door from swinging open. Lock tongues of this type are typically spring biased towards the extended position. Therefore, in such locks, the lock tongue will normally extend out into the extended position except when the lock is operated (e.g. by operating the handle or a key) to retract the tongue. This means that the lock tongue will typically extend out from the lock in the extended position even when the door is open or ajar. Therefore, to prevent damage to the lock tongue or the doorjamb when the door swings closed, linearly reciprocating lock tongues of this type typically have an angled or bevelled outer end. The angled/bevelled end functions such that when the door swings closed and the extended lock tongue collides with the strike, it is the angled/bevelled portion which contacts the strike and this creates a camming action which forces the lock tongue back into the lock so that the door can swing fully closed. (When the door is again fully closed, the lock tongue again extends back out into a cavity in the strike to prevent the door from swinging open).
One problem with the general lock tongue arrangements described in the previous paragraph is that, whilst the lock tongue prevents the door from swinging open when it is extended and engaged with the strike in the doorjamb, such linearly reciprocating lock tongues provide little (if any) resistance to unauthorised attempts to gain entry/passage by forcing the lock to separate or move laterally away from the doorjamb/strike. One example of such “forcing” might be an attempt to force the lock away from the doorjamb using a pinch bar or crowbar. This form of forcing has been termed “jimmying”. If such an attempt were made, and if the lock could be forced to move laterally sufficiently far away from the doorjamb to draw the lock tongue entirely out of the strike, the door could then simply swing open. In this situation, the lock tongue would provide virtually no resistance to this and would simply slide out of the strike. Another way the door might be “forced” is by kicking or otherwise applying a significant force to the panel of the door (the direction of the force being approximately perpendicular to the plane of the door). Such a force could cause the door to deform sufficiently that the lock (or indeed a significant portion of the door edge) moves far enough away from the doorjamb to draw the lock tongue out of the strike. In both of these situations, the lock tongue would simply slide out of the strike. Attempts have been made to alleviate this problem somewhat by cutting or forming notches in the sides of the lock tongue (the intention being that the notches will catch on the strike and help to resist the lock tongue from simply sliding out of the strike in the event of “jimmying” or the like). However, such notches are inadequate to properly address this problem.
Another problem with the above-mentioned bevelled reciprocating lock tongue arrangements is that use of the bevelled lock tongue typically results in the lock being inherently handed. This is because the sloped/bevelled portion of the lock tongue necessarily faces towards one side of the lock and not the other. (Locks rarely, if ever, have sloped/bevelled portions on the lock tongue facing in both directions, because this would reduce the level of security provided by the lock). Therefore, locks incorporating bevelled reciprocating lock tongues generally cannot be installed in doors having the opposite handedness to that for which the lock was originally intended, at least not without reconfiguring the lock so that the sloped/bevelled portion of the lock tongue faces the other way (and for many locks this may not be possible).
It is considered desirable to address or at least partially alleviate one or more of the above-mentioned problems, or to at least provide an alternative to existing locks in the marketplace.
It is to be clearly understood that mere reference herein to previous or existing products, practices or other information, or to any associated problems or issues, does not constitute an acknowledgement or admission that any of those things, individually or in any combination, are admissible prior art or formed part of the common general knowledge of those skilled in the field.